Ball - Early term for "bullet" due to the shape of the earliest projectiles being round lead balls. Still used in military nomenclature, usually to describe a full-metal jacketed bullet.


Ball Powder - Trademarked name for a double-base smokeless propellant powder developed by Olin, Inc. Both spherical or flattened spherical shapes are made..


Ballistic Coefficient (BC) - Ratio of the sectional density of a bullet to its coefficient of form. Represents the projectile's ability to overcome the resistance of the air in flight. A bullet with a numerically high BC will meet less air resistance that a bullet with a low BC


Ballistics - The science of projectiles in motion. Divided into interior ballistics— covering the time between the start of primer ignition and the bullet's exit from the barrel; exterior ballistics—the bullet's movement from barrel exit to target impact; and terminal ballistics —the bullet's behavior from the moment it enters its target until it stops moving.


Barrel-cylinder Gap - The clearance between barrel and cylinder in a revolver. In the U.S., the industry specification is 0.001" to .012". Revolvers with gaps larger that .012" can suffer a bullet lodged in the bore due to excessive gas loss through the over-spec gap.


Battery Cup - Type of primer in which anvil and primer cup are supported in an outside cup. Shotshell primers are of this type.


Bearing Surface - The portion of a bullet's surface that actually touches the bore in moving through the barrel.


Bedding - Manner in which the barrel and action of a rifle is fitted to the stock.


Bell - To expand the mouth of a case slightly in order to seat a bullet more easily. Also called flare.


Belted Case - Case head type with a raised band or belt at the base ahead of extractor groove. A variant of the rimless case. The belt acts to control headspace of the cartridge. See rim and rimless.


Bench Rest - A solid table or bench used for supporting a gun when testing for accuracy. Bench Rest target shooting has become an important shooting sport where the smallest group wins.


Berdan - A centerfire priming system characterized by an anvil mounted in the case's primer pocket with one to three small, off-axis flash holes. Berdan primers have no anvil as the anvil is integral with the case. Poorly suited to reloading. Common in Europe, especially in military ammunition. Named for the inventor, Col. Hiram Berdan, an American.


Black Powder - The oldest ballistic propellant for muzzle loaders and early cartridge arms composed of a mechanical mixture of potassium nitrate (saltpeter), charcoal and sulfur.


Boat Tail - Name given to a bullet type with a tapered base due reduce aerodynamic drag.


Body (of a case) - The section of a bottleneck cartridge case between the head and the shoulder that contains the powder.


Bolt - The locking and cartridge-supporting mechanism of a firearm that operates in line with the axis of the bore. It contains the firing pin, firing pin spring, extractor(s) and sometimes the ejector.


Bolt Thrust - The force on the face of the bolt or breech of a firearm caused by the pressure of burning powder gases. Bolt thrust acts on an axis parallel to the bore.


Bore - The inside of the barrel of a gun of any kind and, in rifled arms, the diameter of the barrel before the rifling is cut.


Bore Sight - To approximately align the sights of the firearm with a target by sighting through the bore.


Boxer - The standard American centerfire priming system, named after the inventor of this type of primer, Col. Edward Boxer of the British Army. Characterized by a large, on-axis flash hole in the case and the anvil mounted in the primer cup. See Primer.


Brass - An alloy of copper and zinc of which cartridge cases are usually made. This term is often applied to empty cartridge cases. Typical cartridge brass has a copper/zinc ratio of 70/30.


Brisance - The characteristic in an explosive of brusqueness or shattering power. The more brisant an explosive, the more rapidly it detonates and the greater its relative power. In small arms, brisance is usually applied to priming compounds.


Bullet - The missile only. Becomes a projectile when in flight. Not to be applied to the term cartridge. See also ball.


Bullet Path - The track followed by a bullet in flight. It is described by the location of the projectile above (+) or below (–) the line-of sight at a given range.


Bullet Pull - The amount of force needed to extract a bullet from a loaded cartridge. Used by ammunition manufacturers to measure uniformity of crimp.


Bullet Puller - A tool for extracting bullets from loaded cartridges. The inertial and collet types are most common.


Burning Rate - A relative term used to rank the rapidity with which a given powder releases energy during burning in comparison with other powders.